Until what time can the Priestly Blessing be recited during Ne'ilah?

Until what time can the Kohanim ascend the platform during the Ne'ilah prayer on Yom Kippur?

Some are strict to perform the Priestly Blessing before sunset, while others permit it until the appearance of the stars [up to thirteen minutes after sunset], and many do not perform the blessing at all.

In the Jerusalem Talmud, Tractate Ta'anit, Chapter 4, it is explained that the hands are not raised at night. See Beit Yosef, Siman 623, which states that for this reason, Ne'ilah should be completed before sunset to allow for the Priestly Blessing. However, the Rema wrote that the custom is not to perform the blessing during Ne'ilah, because the prayer was often extended past nightfall, and therefore the custom in many places is not to perform the blessing at all during Ne'ilah, even in places where it is completed before sunset, to avoid the mistake of performing it at night. Some do perform the blessing during Ne'ilah, and there are places that hurry to complete before sunset, and there are places where the blessing is performed even during twilight [up to thirteen minutes after sunset], because it is explained in Sha'ar HaTziyun, Subparagraph 11, that during twilight, it might be permissible to rely on leniency and perform the blessing, and it concludes there that this requires further study, so there are those who are lenient and perform the blessing during twilight. It should be noted that the Birkei Yosef brings opinions that hold that even if the prayer extends into the night and the time of the appearance of the stars has arrived, the blessing can still be performed. See Kaf HaChaim, which brings many authorities who hold this view, and it is difficult to rely on this opinion since the Mishna Berura and Magen Avraham ruled not to perform the blessing at night at all.